Long-term heavy alcohol consumption is the leading cause of illness and death from liver disease in the Western world. Alcoholic liver disease (ALD) is well characterized clinically and morphologically and is described in three major stages of disease progression: 1) fatty liver, which is usually reversible with abstinence, 2) alcoholic hepatitis or liver inflammation, and 3) cirrhosis, or scarring of the liver. Novel therapeutic tools are needed for the treatment of ALD. However, to develop such therapies, a thorough understanding of the molecular mechanisms contributing to each stage of alcohol-induced liver injury is required. Recent developments in high-throughput technologies make the global profiling of differentially expressed gene products a reality. We propose to develop a quantitative proteomic strategy to identify the molecular mechanisms contributing to the development of ALD. Because the molecular mechanisms underlying each of the three clinical stages of disease progression are still poorly understood, we will focus on disease biogenesis: 1) the determination of the molecular mechanisms contributing to ALD Stage 1, alcoholic fatty liver disease (AFLD), 2) the dissection of the mechanisms specifically attributed to the use of alcohol by a comparative analysis with nonalcoholic fatty liver disease (NAFLD), and 3) the subsequent selection/characterization of protein biomarker candidates which can distinguish between alcoholic and nonalcoholic fatty liver and lead to the establishment of signature diagnostic panels for early disease progression.